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  • Analytical Chemistry and Spectroscopy  (180)
  • ASTROPHYSICS
  • Inorganic Chemistry
  • 1995-1999  (288)
  • 1945-1949  (7)
Collection
Keywords
Publisher
Years
Year
  • 1
    Electronic Resource
    Electronic Resource
    GC-MS determination of catechin and epicatechin levels in human plasma (1997)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 621-623 
    Details
    ISSN: 0935-6304
    Keywords: GC-MS ; Catechin ; Epicatechin ; Flavonoids ; Plasma ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240201111
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  • 2
    Electronic Resource
    Electronic Resource
    Conformational and configurational study of 1,3-dioxolanes by proton and carbon NMR spectroscopy (1995)
    Chichester : Wiley-Blackwell
    Organic Magnetic Resonance 33 (1995), S. 167-173 
    Details
    ISSN: 0749-1581
    Keywords: 1,3-dioxolanes ; NOE ; vicinal proton-proton coupling ; configurational analysis ; conformational analysis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The configurational and conformational properties of six 4-trimethylammoniummethyl 2,2-disubstituted 1,3-dioxolanes were studied using NOE experiments and vicinal coupling constants. Selective 1D NOE experiments proved to be effective tools in the configurational assignment of C-2 relative to C-4. The preferred conformation of the dioxolane ring and the exocyclic group at C-4 was obtained by employing vicinal coupling constants and NOE results. The 1H and 13C NMR chemical shifts show stereochemically dependent trends. Quantitative analysis of conformer populations was performed using Haasnoot et al's equation. The —N+(CH3)3 group was found to be synclinal with respect to the heterocyclic O-3 atom and points outside the ring. When a phenyl group is present at C-2, the 4-CH2N+ -  group in a trans relationship to the 2-phenyl ring was found to occur prevalently in a pseudo-axial orientation, whereas it was established to be prevalently pseudo-equatorial when cis with respect to the phenyl ring.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mrc.1260330303
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  • 3
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    BATSE observations of gamma-ray burst spectra. 2: Peak energy evolution in bright, long bursts (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: We investigate spectral evolution in 37 bright, long gamma-ray bursts observed with the Burst and Transient Source Experiment (BATSE) spectroscopy detectors. High-resolution spectra are chracterized by the energy of the peak of nu F(sub nu), and the evolution of this quantity is examined relative to the emission intensity. In most cases it is found that this peak energy either rises with or slightly precedes major intensity increases and softens for the remainder of the pulse. Interpulse emission is generally harder early in the burst. For bursts with multiple intensity pulses, later spikes tend to be softer than earlier ones, indicating that the energy of the peak of nu F(sub nu) is bounded by an envelope which decays with time. Evidence is found that bursts in which the bulk of the flux comes well after the event which triggers the instrument tend to show less peak energy variability and are not as hard as several bursts in which the emission occurs promptly after the trigger. Several recently proposed burst models are examined in light of these results and no qualitative conflicts with the observations presented here are found.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 439; 1; p. 307-321
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    The unusual helium variable AM Canum Venaticorum (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The unusual variable star AM CVn has puzzled astronomers for over 40 years. This object, both a photometric and spectroscopic variable, is believed to contain a pair of hydrogen-deficient white dwarfs of extreme mass ratio, transferring material via an accretion disk. We examine the photometric properties of AM CVn, analyzing 289 hours of high-speed photometric data spanning 1976 to 1992. The power spectrum displays significant peaks at 988.7, 1248.8, 1902.5, 2853.8, 3805.2, 4756.5, and 5707.8 microHz (1011.4, 800.8, 525.6, 350.4, 262.8, 210.2, and 175.2 s). We find no detectable power at 951.3 microHz (1051 s), the previously reported main frequency. The 1902.5, 2853.9, and 3805.2 microHz peaks are multiplets, with frequency splitting in each case of 20.77 +/- 0.05 microHz. The 1902.5 microHz seasonal pulse shapes are identical, within measurement noise, and maintain the same amplitude and phase as a function of color. We have determined the dominant frequency to be 1902.50902 +/- 0.00001 microHz with dot P = +1.71 (+/- 0.04) x 10(exp -11) s/s. We discuss the implications of these findings on a model for AM CVn.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 445; 2; p. 927-938
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Chromospheric variations in main-sequence stars (1995)
    In:  Other Sources
    Details
    Publication Date: 2019-08-28
    Description: The fluxes in passbands 0.1 nm wide and centered on the Ca II H and K emission cores have been monitored in 111 stars of spectral type F2-M2 on or near the main sequence in a continuation of an observing program started by O. C. Wilson. Most of the measurements began in 1966, with observations scheduled monthly until 1980, when observations were schedueld sevral times per week. The records, with a long-term precision of about 1.5%, display fluctuations that can be idntified with variations on timescales similar to the 11 yr cycle of solar activity as well as axial rotation, and the growth and decay of emitting regions. We present the records of chromospheric emission and general conclusions about variations in surface magnetic activity on timescales greater than 1 yr but less than a few decades. The results for stars of spectral type G0-K5 V indicate a pattern of change in rotation and chromospheric activity on an evolutionary timescale, in which (1) young stars exhibit high average levels of activity, rapid rotation rates, no Maunder minimum phase and rarely display a smooth, cyclic variation; (2) stars of intermediate age (approximately 1-2 Gyr for 1 solar mass) have moderate levels of activity and rotation rates, and occasional smooth cycles; and (3) stars as old as the Sun and older have slower rotation rates, lower activity levels and smooth cycles with occasional Maunder minimum-phases.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 438; 1; p. 269-287
    Format: text
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    NASA TECHNICAL REPORTS
  • 6
    Electronic Resource
    Electronic Resource
    Column liquid chromatography coupled on-line with mass spectrometry using post-column phosphate suppression (1995)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 45-48 
    Details
    ISSN: 0935-6304
    Keywords: Column liquid chromatography ; On-line phosphate suppression ; On-line mass spectrometry ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The coupling of column liquid chromatography on-line with mass spectrometry using post-column phosphate suppression is described. A membrane suppressor is used to remove the non-volatile phosphate ions from the mobile phase after the chromatographic separation prior to introduction into the mass spectrometer. Using post-column phosphate suppression by a membrane device phosphate concentrations up to 10 mM phosphate, at a mobile phase flow rate of 0.1 ml/min, could be removed for more than 99% without any decay of the sensitivity of the MS detection.Using a new antidepressant tetracyclic basic compound, ORG 4428, and some structure related compounds as model compounds electron impact as well as chemical ionisation spectra of all compounds could be obtained. The set-up could be used for several weeks running, using a phosphate containing mobile phase, without any loss of performance.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240180110
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  • 7
    Electronic Resource
    Electronic Resource
    Revisit of MALDI for small proteins (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1315-1320 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Matrix-assisted laser desorption/ionization (MALDI) was used for several small proteins (such as insulin) and for peptides. It was found that the detection efficiencies of MALDI for the insulin B chain and the insulin A chain are drastically different. Similar phenomena were also observed for various types of peptides. The positive-ion signal of MALDI in detecting proteins or peptides was found to be greatly enhanced by the presence of a basic amino acid in their chains. The experimental results indicate that this enhancement may arise from proton transfer in solution by an acid-base reaction between the protein/peptide and matrix molecule. This pre-protonated mechanism provides a low energy barrier for the ionization of peptides in a MALDI process, and greatly reduces the energy threshold of MALDI. Matrix effects on the ionization mechanism are discussed.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091318
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  • 8
    Electronic Resource
    Electronic Resource
    Detection of high molecular weight starburst dendrimers by electrospray ionization mass spectometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1552-1555 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: An entire series of Starburst polyamidoamine (PAMAM) dendrimers consisting of generations 1 through 10 (G1-10) have been studied by positive-ion electrospray ionization mass spectrometry (ESI-MS) using an extended m/z range quadrupole mass spectrometer. Charge-state distributions were detected as high as m/z 12 000 for the generation 10 dendrimer, having a theoretical molecular weight of 1 megadalton and containing approximately 93 maximum positive charges on the molecule. Accurate molecular weight determinations of the smaller generation dendrimers (G1-3, Mr ∼ 1.4kDa to 6.9kDa) were obtained using a commercial triple quadrupole instrument. The unit resolution ESI mass spectra provide information on the number of incomplete reactions which may occur during polymer synthesis. The extent of gas-phase charging observed by ESI-MS on the entire series of macromolecules was found to exhibit a linear relationship to Mr2/3, consistent with theoretical models prediciting a spherical ion structure with maximum charging controlled by Coulombic effects.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091516
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  • 9
    Electronic Resource
    Electronic Resource
    Detection of ΔF508 mutation of the cystic fibrosis gene by matrix-assisted laser desorption/ionization mass spectrometry (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 772-774 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The most common mutation of the cystic fibrosis gene is characterized by the deletion of three nucleotides that code phenylalanine in the 508 position of the cystic fibrosis transmembrane conductance regulator. We report the first measurements by matrix-assisted laser desorption/ionization (MALDI) time-of-flight mass spectrometry for the ΔLF508 mutation in cystic fibrosis carriers and patients. Furthermore, in a blind test, results from the normal and ΔLF508 mutant alleles in 30 clinical samples based on MALDI mass spectrometry and on conventional gel analysis of the DNA were in total agreement. These results demonstrate the utility of MALDI mass spectrometry in the molecular diagnosis of mutant alleles and point to its potential use for ultra-fast detection in large-scale screening of DNA mutations.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290090910
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  • 10
    Electronic Resource
    Electronic Resource
    High temperature mass spectrometric study of the B2O3—Al2O3 system at 1248-1850 K (1995)
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 1244-1251 
    Details
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The high-temperature mass spectrometric Knudsen effusion method has been used to study the vaporization processes and thermodynamic properties of the B2O3—Al2O3 system in the temperature range 1248-1850 K. Data on the B2O3 partial vapour pressures and the B2O3 activities in the system under consideration were obtained. The enthalpies of formation of Al4B2O9 and Al18B4O33 have been evaluated from the values of the enthalpies of B2O3 sublimation from boron oxide and from these compounds. Comparison is made between the available phase diagram of the B2O3—Al2O3 system and the results obtained in the present study, using the complete isothermal vaporization method.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/rcm.1290091306
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